1. Technical Field
The present invention relates to an inverted organic electronic device and a method for manufacturing the same. More particularly, the present invention relates to a method for manufacturing an inverted organic electronic device, which includes a process of forming a bilayer or composite layer of a cathode interface layer and a photo active layer through coating a cathode interface material and a photo active material onto a substrate only once, and an inverted organic electronic device manufactured thereby.
2. Description of the Related Art
An organic solar cell is a representative organic electronic device and spotlighted in the art as a next generation energy source with various advantages, such as low cost, flexibility, light weight, portability, easy attachment to a curved surface of a building, and the like. In addition, the organic electronic device attracts much attraction by permitting mass production through a printing process that requires lower cost and allows more rapid production rate than vacuum deposition.
The organic solar cell generally has a structure of “substrate/first electrode/interface layer/photo active layer/interface layer/second electrode”, in which the interface layers are used to maximize efficiency of the organic solar cell. The most well-known organic solar cell (conventional structure) has a structure of substrate/first electrode/anode interface layer/photo active layer/cathode interface layer/second electrode. On the contrary, as disclosed in Korean Patent Publication No. 2013-0037569A, a solar cell including a first electrode formed on a substrate and an electron transport layer formed on the first electrode is called an inverted organic solar cell, and has a structure of substrate/first electrode/cathode interface layer/photo active layer/anode interface layer/second electrode. Such an inverted organic solar cell has higher stability and allows easier printing than an existing organic solar cell structure and thus attracts attention particularly as a commercially available structure.
In the inverted organic solar cell, the cathode interface layer provides a very important function. Generally, as the first electrode on the substrate, for example, as a cathode, a transparent electrode is used in the art. However, most transparent electrodes (for example, indium tin oxide (ITO)) have high work function and thus are not suitable for collection of electrons generated in the photo active layer. Here, when the cathode interface layer is formed on the cathode, it is possible to achieve significant reduction in work function of the cathode while facilitating collection of electrons. Such a cathode interface layer may be composed of metal oxides, conjugated polyelectrolytes, metal carbonates, self-assembly monolayers, non-conjugated polymers, and the like.
However, since such a cathode interface layer has a film thickness of a few nanometers to dozens of nanometers in an optimized inverted solar cell, it is very difficult to form the cathode interface layer in the form of a uniform and pinhole-free thin film and there is a need for an additional process that is accurate and expensive.